Succession in the Microflora of Leaves and Litter of Three Plant Species at Sub-Antarctic Macquarie Island

Abstract

Microbial ecology and succession were studied on leaves and litter of Poa foliosa, Stilbocarpa polaris, and Pleurophyllum hookeri which are the three dominant species of flowering plant of the Sub-Antarctic herbfields of Macquarie Island. Colonization was monitored on sample plots, with particular reference to the occurrence of filamentous fungi. The leaves and litter were examined by microscopic observation, and from cultures obtained after serial washing or surface sterilization. The patterns of microbial succession were similar for the three plant species and resembled those on most plants from temperate and tropical regions, except that on Macquarie Island most primary saprophytes became established on leaves before senescence. Despite similarity as to the types of micro-organisms and classes of filamentous fungi occurring at certain stages of the succession, there were obvious differences both between the three plant species and in comparison with plants from other parts of the world in the fungal species involved. The main differences referred to the fungal species which dominated the primary saprophytic microflora. These were Ascomycetes with Coelmycete anamorphs, which were often either host-specific or host-restricted, and included unidentified and probably new species of Phoma (3 spp.) and Mycosphaerella (1 sp.), and Ascochyta stilbocarpae. The Phoma spp. and Mycosphaerella sp. are restricted, as far as is known, to Macquarie Island. Other primary saprophytes, including Mycosphaerella tassiana and Leptosphaeria eustoma occur worldwide, but appear to favour cold climates.